I've had trouble 2x this year with my nexus 8, older milano semi-horizontal dropout bike's rear wheel slipping in the drive side drop out. (Maybe I'm just getting stronger?-Not likely!)

15,000 miles on the bike. Why the trouble now? Maybe I'll have to start carrying a longer wrench for the wheel nuts so I can get them tight enough.

I would, however, rather carry a bigger wrench than have a chain tensioner on this bike.
The Nexus8 hub has proven VERY reliable to me in all weather conditions.